The wind event of December 2011 is certainly the most devastating to our tree canopy I have seen in my personal management of business in the last 30 years.
Will routine maintenance make a tree more survivable in a wind event? Trees which needed to be pruned suffered more loss than those which are regularly maintained. One of our company strengths is to plan recurring maintenance for our tree clients, which is dependent upon the tree tolerance of stress by species and the likelihood of breakage causing damage to their environment. There is evidence in this storm of trees of the same species and size, in the same location that supports this program’s assertion that maintenance helps to preserve trees. Three huge ficus pruned a month ago had a couple of minor broken limbs. Two other ficus in the same setting which were not pruned for a couple of years suffered devastating breakage to more than half of their canopy. Keep in mind the damaged trees were under maintenance but just not recently pruned. No one knows when historic winds might hit.
So while that experience may be good testimony for the value of maintenance, I cannot honestly say that was the only observation in the wind of last week. Many factors affect wind damage. Direction, duration, and intensity of the wind are obvious and more damaging the more variable these factors. Root stability in wind is affected by root health, soil type, soil moisture content, and available volume for the roots to grow. The tree itself maybe well maintained but of advanced age or growing in adverse conditions but in a more sheltered environment. It could survive or fail on any one of these factors.
A second consideration asks, should some trees be removed at some point in their life to prevent failure? Wearing my engineer hat I must agree when there are observable symptoms of structural risk, or there are extrapolated conclusions based on environmental conditions to predict higher risk of failures. In fact, engineer mentality can only give a risk free assessment when all trees are removed.
But then putting on my tree-lover hat I assume that some risk is tolerable and try to balance the many benefits of the tree with the potential to do damage if failure occurs. When deciding to retain a tree, the person making that decision should do so with an acceptance of tolerable level of risk. A competent Registered Consulting Arborist or experience Certified Arborist should always be involved in making any risk assessment.
So bottom line, what did we see in this storm? While maintained trees may have sustained less damage in a similar environment of conditions and exposure, overall damage may not have been maintenance related. An appropriately thinned pine or oak was toppled due to unbuffered exposure to intense wind speed, high soil moisture or restricted root volume. A structurally unsound specimen with dense unpruned growth and dead wood was unscathed in a more sheltered environment with dry soil or well developed roots. My own California pepper, well maintained at our office, lost its top due to wind acceleration across the roof of my building…and the debris remains in the yard until we can serve more than a hundred calls for help.
And one word of caution:
don't over-react out of fear that another wind may come and cause a tree disaster in you yard. Sadly the ill informed or easily convinced often remove or top perfectly sound and valuable trees following such disasters. If yours did not fall over in a recent heavy rain, or break in this wind there is a good chance it is pretty sound. Call a credentialed professional for an evaluation.